1. Field Of The Invention
This invention relates to autotrack antenna systems and, more particularly, to a simulation technique for testing autotrack antennas.
2. Discussion
Many communication systems require high gain reflector antennas for acquiring and tracking a signal. An autotrack system is generally employed to keep the antenna pointed in the direction of the incoming signal, which, for communication satellites and the like, changes as a function of time because of the changing position of the antenna in relation to the source of the signal.
Generally, an autotrack antenna employs a sum pattern and a difference pattern. In some cases, the antenna may employ two orthogonal difference patterns for azimuth plane and elevation plane error sensing. The sum pattern is a high-gain/pencil-beam used for transmit and receive communications. The difference pattern under receiving conditions provides error signal voltages that are proportional to the angle of arrival of the incoming wave, relative to the boresight axis of the reflector. A servo control system is employed to steer the reflector antenna so as to cause the error voltages to vanish, which occurs when the boresight axis is pointed at the transmitting terminal of the incoming signal.
The testing of autotrack antenna systems is generally required to provide for accurate verification of autotrack direction angle sensing for a selected set of incident plane-wave directions. Currently, autotrack antenna systems are normally tested under receive conditions on a far-field antenna range, which is a test environment representative of operational conditions. However, such testing requires that each autotrack antenna system be transported to and set up with the far-field antenna range. As a result, a considerable amount of time and expense are generally required.
It is therefore desirable to obtain a simplified or alternate technique for testing autotrack antennas. It is further desirable to obtain such a testing technique which provides substantial cost savings by reducing the time required to perform the testing.